I am studying the conceptual foundations of medicine for the period approximately 1670 to 1740. This was the period when the atomistic philosophy seemed to replace the older Platonic-Aristotelian formulations. But in many areas of medicine, particularly those areas concerned with the "mind," the replacement was often more apparent than real. In my studies I pay particular attention to such concepts as Nature, Witchcraft, Archeus, imagination, soul, reason, and the intimate connections between these and medical doctrines. I also study the methodological problems concerned with rationalism and empiricism, analogy, scientific method, critical evaluations, as these developed in the early 18th century. All of these concepts are concretely related to the important physicians and biologists and "natural philosophers" of the era.